1. Field of the Invention
The present invention relates to a programmable digital entertainment terminal (DET) for use in digital video program distribution networks providing dynamic programming of such a terminal to offer a variety of broadcast and interactive services.
2. Description of the Related Art
Set top terminal devices are interface devices used to process broadband signals received at a customer premises before being supplied to a user's television set for viewing. Such set top terminal devices are commonly supplied by cable television companies to their subscribers and are used to receive the RF signals from the cable television distribution systems.
Despite their popularity in the cable television industry, these cable television terminal devices have a number of limitations. For example, the cable television terminal devices are limited to processing of analog television signals. In addition, cable television terminal devices are generally "dumb" devices having a limited set of functionalities constrained by the hard wired programming of the internal micro-processor controlled device. Essentially all cable television terminal devices respond to a selection input from the subscriber, tune to a selected channel available on the cable television network, decode the video program material if scrambled, and provide output signals compatible with a standard television receiver.
Enhanced cable television terminals do provide some additional features, such as graphics overlay capability and two way communication of control signaling to and from headed terminal devices. Although such improved terminals facilitate some enhanced services, such as home shopping and purchasing, the performance of these cable television set top terminals is still limited to analog decoding. Further, the range of services remains limited by the hard wired capabilities of the microprocessor within the set-top terminal devices.
Proposals have been made to download computer executable code over cable television networks. In particular, U.S. Pat. Nos. 5,051,822 and 5,181,107 both to Rhoades disclose a terminal device connectable to a cable television network and a telephone line. A subscriber requests a video game or other software stored in a remotely located software storage center by operating the terminal to establish a bidirectional telephone link with the remote storage center. The center transmits the encoded software program together with the terminal identification code as a digital bit stream over a Television broadcast channel. The terminal requesting the software monitors all digital bit streams on the broadcast channel but receives only the software program addressed to it, i.e. only after identification code validation occurs. Once reception of all the software data is complete, the terminal acknowledges receipt to the remote storage center and drops the telephone line. The encoded software program is decoded, and the terminal provides a display informing the subscriber that the game or other program is ready for use. The terminal also offers the subscriber the means to interact with the software, e.g. play the game, using contemporary gaming control or input devices.
While the Rhoades terminal structure does provide enhanced capabilities, such as video games and home shopping, the display functionality controlled by the downloaded software is limited to computer displays generated in response to the software. Hence, there is no direct interaction of the received software with any video program carried on the cable network, nor does the downloaded software control any further instructions with the storage center. Since the video transmissions on the cable system are analog, a separate telephone connection is required for selection inputs to the central storage facility. Furthermore, the terminal device apparently can receive software from the storage center of only one service provider.
While some prior art systems permit downloading into the cable television decoder itself, this downloading of information into the decoder has apparently been limited to information controlling the decoding of the television program signals, e.g. a key word used in a descrambling algorithm. For example, Dufresne et al., in U.S. Pat. No. 4,623,920 each a specific scheme for addressing data transmissions over a cable television network to groups of terminals or to individual terminals. The addressed data sent from the head end can include an option table of signals for controlling descrambling of available television programs, data to enable operation of a cable TV converter, or software for operating a peripheral microcomputer separate from the cable television terminal device. The Dufresne et al. terminal is limited to reception of data from only one service provider, i.e. the provider operating the cable TV network. Also, the services provided through the terminal are limited in that the downloaded data apparently does not alter or control the terminal functionality for further interactions with the provider through the network.
Recently, several different wideband digital distribution networks have been proposed for offering subscribers an array of video services, such as Video On Demand. These services, also referred to as video dial tone services, are designed to enable users to select desired programs from multiple video information providers (VIPs). The following U.S. Patents disclose representative examples of such digital video distributions networks: 5,253,275 to Yurt et al., 5,132,992 to Yurt et al., 5,133,079 to Ballantyne et al., 5,130,792 to Tindell et al., 5,057,932 to Lang, 4,963,995 to Lang, 4,949,187 to Cohen, 5,027,400 to Baji et al., and 4,506,387 to Walter. The terminal devices in these digital networks are still limited functionality devices. In these networks, the digital terminal devices still only receive selection inputs, transmit selection signals upstream to the source of the video materials, receive downstream video transmissions, decompress the digitized video materials and convert to analog form, and provide appropriate signals to a television receiver.
One such digital video distribution network and the terminal device for such a network, is disclosed in Litteral et al. U.S. Pat. No. 5,247,347, the disclosure of which is hereby incorporated in its entirety into this disclosure by reference. Litteral et al. discloses an enhanced public switched telephone network which also provides a video on demand service to subscribers over the Public switched telephone network. A menu of video programming information is displayed at the subscriber's premises by a set-top terminal and a TV set. The subscriber may transmit ordering information via the Public switched telephone network to the independent video information providers. Video programming may be accessed and transmitted to the subscriber directly from a video information provider (VIP) or through a video buffer located at a central office (CO) serving the subscriber.
The above detailed discussion of the Litteral et al. system shows that prior art digital distribution networks offer enhanced video services, but the terminal device functionality is still limited to program selection, decoding and display. Also, the interactive services provided require a full wideband channel to each DET, dedicated entirely to that DET, for the entire session.
A number of suggestions have been made in the press regarding arrays of different services which will become available through broadband digital networks now popularly referred to as the "Information Super Highway". If a different VIP were to offer a different service, the VIP can limit the service to an interactivity with the subscriber essentially corresponding to the functionality available in the terminal device. This approach, however, limits the functional capabilities the new VIP may choose for the different service. Alternatively, the subscriber must buy another terminal device programmed or wired to function in accord with the VIP's new service. This second approach, however, forces the subscriber to purchase and connect a different terminal device for each subscribed service.
An additional problem of the known terminal devices is that the terminal device is limited in compatibility to the functions specified by the information provider during hard-wiring of the terminal device. Moreover, the conventional terminal devices are dedicated in functionality to support the interactive session until the session is terminated by the user or the information provider. Since the interactive session typically requires a large amount of bandwidth to download interactive video data, the interactive session will usually occupy the entire downstream bandwidth allotted to a user, thereby preventing the user from accessing other video dial tone services during the interactive session. Thus, the user is "locked into" the interactive session and unable to access other video dial tone services. This problem may be a substantial annoyance to users when the interactive sessions are extremely lengthy.